Fuel-metering unit for internal combustion engines

ABSTRACT

A fuel-metering unit adapted for use in an internal combustion engine having an exhaust pipe is described which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an air-measuring device mounted in the suction tube upstream of the throttle valve, by-pass means connected with the suction tube and bypassing the air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through the suction tube. This unit is improved by providing control valve means associated with the by-pass means and adapted for controlling the by-pass means and thereby varying the proportionality of fuel and air in dependence on characteristic engine data, and by providing an exhaust gasmeasuring probe adapted for mounting in the exhaust pipe of the engine and adapted for controlling the control valve means.

United States Patent 1 [111 3,

Stumpp Dec. 23, 1975 15 1 FUEL-METERING UNIT FOR INTERNAL 3.783.846 H1974 Barnhart et a1 123/117 A COMBUSTION ENGINES 3.791359 2/1974 Eckert et a1. 123/119 R [75] Inventor: Gerhard Stumpp, Stuttgart, Germany [73] Assignee: Robert Bosch G.m.b.H., Stuttgart,

Germany [22] Filed: June 18, 1973 [21] Appl. No.: 370,826

[30] Foreign Application Priority Data Aug. 25. 1972 Germany 2241936 [52] US. Cl 123/119 R; 60/276; 60/285; 123/139 AW; 123/140 MC; 123/140 MP [51] Int. Cl. F02M 7/00; FOZM 69/00 [58] Field of Search. 123/140 MP, 140 MC, 119 D, 123/119 DB, 119 R, 32 EA; 60/276, 285

[56] References Cited UNITED STATES PATENTS 1.761.513 6/1930 Arthur 123/117A 3,721,222 3/1973 Shioya 123/119 D X 3.738.343 6/1973 Zeyns et 123/119 R 3,745,768 7/1973 Zechnall et 123/32 EA X 3,759,232 9/1973 Wahl et a1. 123/32 EA 3,777,725 12/1973 Stumpp et al 123/119 R Primary Examiner-Charles J. Myhre Assistant Examiner-Tony Argenbright Attorney, Agent, or Firm-Edwin E. Greigg [5 7] ABSTRACT A fuel-metering unit adapted for use in an internal combustion engine having an exhaust pipe is described which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an airmeasuring device mounted in the suction tube upstream of the throttle valve, by-pass means connected with the suction tube and bypassing the air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through the suction tube. This unit is improved by providing control valve means associated with the bypass means and adapted for controlling the by-pass means and thereby varying the proportionality of fuel and air in dependence on characteristic engine data, and by providing an exhaust gas-measuring probe adapted for mounting in the exhaust pipe of the engine and adapted for controlling the control valve means.

8 Claims, 5 Drawing Figures 1 [II/ I71 US. Patent Dec. 23, 1975 Sheet 1 of 3 3,927,649

U.S. Patent 1:66.23, 1975 sheetzom 3,927,649

US. Patent Dec.23, 1975 Sheet3of3 3,927,649

FUEL-METERING UNIT FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION The invention relates to a fuel-metering unit for externally ignited internal combustion engines, which unit comprises a suction tube for the intake of air in which an air-measuring device and a randomly adjustable throttle valve are arranged in sequence, and in which an essentially proportionate amount of fuel is metered into the amount of air flowing therethrough, the proportionality of the fuel amount being adjustable by means of controlling a by-pass circumventing the. air-measuring device in dependence on engine data. Fuel-metering units are already known, in which this proportionality between fuel amount and air amount is adjustable in dependence on engine data, in which, however, an optimal ratio in the mixture cannot be attained as, even though the same rate of air flow prevails at several operating levels in the engine performance graph, the requirements with regard to the airfuel mixture differ therefrom. These differing requirements are particularly critical in the case, when a detoxification of the exhaust gases is to be achieved through adjustment of the proportionality of the fuel and air amounts.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to improve the aforesaid known fuel-metering unit so as to achieve an adjustment of the fuel/air mixture by means of a simple device in which, as far as possible, no toxic components will form in the exhaust gas.

This object is attained according to the invention by providing in the initially described fuel-metering unit a valve which is arranged in the aforesaid by-pass, the passage through which valve is controlled by an exhaust gas-measuring probe built into the exhaust pipe of the engine; the exhaust gas-measuring probe is preferably designed as an oxygen-measuring probe which responds to the partial pressure of oxygen in the exhaust gases. Thereby it is possible to obtain for every imaginable engine condition a proportionality between the amount of fuel and air which corresponds to the air number A=l.

In a preferred embodiment of the invention, the measuring probe influences a solenoid controlling the bypass valve, and the working stroke of the solenoid advantageously corresponds to the applied amperage.

In another embodiment of the invention, the by-pass valve is actuated pneumatically via a control conduit which opens out into the suction tube and into which a solenoid valve controlled by the exhaust gas measuring probe is interposed. In this case the by-pass valve can be designed as a membrane valve having a pressure chamber in which the aforesaid control conduit opens, and opposite the opening of the said control conduit, there opens another conduit which leads to the surrounding atmosphere. Between the openings of these two conduits, the free end of a leaf spring is arranged which spring constitutes a flexible valve member, in the pressure chamber, which controls the openings of the aforesaid two conduits and which can be actuated by means of the above-mentioned solenoid. A membrane valve of this type can serve as a pneumatic integral action control means capable of controlling a proportionality change of up to 20%.

According to another advantageous embodiment of the invention, the by-pass opens out upstream of the throttle flap in the suction tube, but still within the immediate range of that part of the throttle flap which moves counter to the air flow, whereby, when the throttle valve is opening, the pressure prevailing in the suction tube downstream of the throttle valve is also acting on the orifice of the bypass. Thereby, it is possible to attain and maintain the same dilution of the mixture with air when opening the by-pass, regardless of the position of the throttle valve. The orifice of the by-pass in the suction tube can advantageously be designed as a throttle, the cross section of which can be chosen as designed, thereby ensuring the same impoverishment of the mixture while the by-pass is open regardless of the rpm of the engine.

The invention will be better understood and further objects and advantages will become apparent from the ensuing detailed specification of preferred but merely exemplary embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in a schematical view a first embodiment of the fuel-metering unit according to the invention,

FIG. 2 shows four different types of throttle orifices for use in the embodiment shown in FIG. 1;

FIG. 3 shows another embodiment of the fuel-metering unit comprising a servo valve actuated via a solenoid valve;

FIG. 4 shows an embodiment similar to that of FIG. 3, but having the solenoid incorporated in the servo valve, and

FIG. 5 shows a part of the air-intake tube and throttle valve arrangement of the preceding figures equipped with control means for the by-pass orifice in the suction tube.

DESCRIPTION AND OPERATION OF THE EMBODIMENTS As shown in FIG. 1, an air-measuring device 2 and a throttle valve 3 are arranged in a suction tube 1 successively in the direction of air flow therethrough (as indicated by arrows). The air-measuring device 2 is, for example, designed as a plate 4 which is disposed to extend transverse to the direction of air flow, and which is attached to a lever 5 in such a manner as to penetrate during its measuring motion into a frustoconical zone 6 of the suction tube, in accordance with an approximately linear function of the amount of air flowing through the suction tube 1. Lever 5, being supported in a bearing as far as possible free from friction, actuates during its swivelling motion the movable valve member 7 of a fuel-metering and distributing valve. The fuel which is present under constant pressure in a fuel line 9 and which is supplied to the metering valve 8 via a branch line 10, acts upon the frontal face (not shown) of the movable valve member 7 and thus serves to reset the plate 4, its resetting force thereby remaining constant.

The supply of fuel takes place via an electrically operated fuel pump 11 which aspirates the fuel from a reservoir 12 and conveys it via line 9 to the metering valve 8. A line 13 having a pressure-regulating valve I4 interposed therein branches off from line 9. The quantitatively metered fuel is distributed by metering valve 8 to individual lines I5 which lead to the individual injection valves (not shown). However, a carburettor or a hot wire measuring member may also serve as the air-metering device 2.

The zones of the suction tube upstream and downstream of the air-measuring device 2 are connected with one another by means of a by-pass 16 which is controlled by means of a control valve 17. The cross sectional area of by-pass 16 is moreover defined by throttle orifice 18 which is devised as a disc and is mounted at the mouth of by-pass 16 opening into suction tube 1. This mouth of by-pass 16 is located in suction tube 1 at a point upstream of the throttle valve 3 when the flap of throttle valve 3 is in closed position. The more the flap of throttle valve 3 is opened, the more will the pressure prevailing in the suction tube downstream of flap 3 have an influence on this mouth and consequently on the pressure in the adjacent portion of by-pass 16.

In the embodiment shown in FIG. 1, control valve 17 is devised as a directly controlling solenoid valve which comprises an armature 20 operable as a movable valve member against the force of a closing spring 21 by energization of an excitable coil 22 about a core 23. Armature 20 is provided with a bore 24 for pressure relief. Excitable winding 22 is energizable by electric current supplied from an amplifier 25 in response to an oxygen-measuring probe 26 which is arranged in an exhaust pipe 27 of the internal combustion engine. The air number It mentioned further above characterizes the composition of the fuel/air mixture, the air number A being equal to 1 when the air/fuel ratio in the mixture is stoichiometric. The ion currents usable for regulation in the oxygen-measuring probe will vary as soon as there is a change in the air number A.

In FIG. 2, various orifice plates 18 are shown having apertures of different designs. Plate 18a has an aperture 29 of circular cross sectional area; in plate18b, the aperture 30 is of oval cross sectional area; in plate 18c the shape of aperture 31 is rectangular; and in plate 18d, two circular apertures 32 are provided which are to be built into the suction tube 1 so as to be arranged one after the other in the direction of air flow,

ln the embodiment shown in H6. 3, control valve 17 is constituted by a pneumatically working servo valve. This valve comprises a valve plate 35 being attached to a membrane 36 and being urged onto a valve seat 38 by means of a closing spring 37. The pressure chamber 39 which houses spring 37 communicates with suction tube 1 by way of a control conduit 40. A solenoid valve 41 is disposed in control conduit 40, and is controlled by measuring probe 26 and amplifier 25 (not shown in this figure). Solenoid valve 41 comprises an armature 42 which is actuated as a movable valve member by energization of a coil 44 against the force of a return spring 43. Solenoid valve 41 operates as a 2:3-way valve, as the movable valve member 42 controls two valve seats 45 and 46. Depending on the position of movable valve member 42, line leading from the pressure chamber 39 to solenoid valve 41 is more or less widely opened for communication either with the portion of line 40 which leads from solenoid valve 41 to the suction tube 1 or with a line 47 opening into the surrounding atmosphere.

In the embodiment shown in FIG. 4, a magnet 50 is incorporated in a servo valve 17. Magnet 50 serves to actuate a leaf spring 51, the free end 52 of which is disposed between the mouths 53 and 54 of two tubes 55 and 56 of which tube 56 constitutes part of a control 4 conduit 40' leading to suction tube 1, while the other tube 55 communicates with the surrounding atmosphere.

FIG. 5 shows a variation of the embodiments described hereinbefore, wherein the free cross sectional area of the mouth 57 of by-pass 16, which mouth is disposed up-stream of throttle valve 3, is controlled by means of a cam disc 58, the rim of which is profiled, the disc 58 being mounted on the shaft 59 of throttle valve 3 in a plane at right angle to the flap thereof so that the disc can be turned together with the flap of throttle valve 3. In this control zone, suction tube 1 can be flattened, or the by-pass tube 16 projects sufficiently into the interior of suction tube 1 to have its mouth 57 open laterally toward and be engaged by cam disc 58.

What is claimed is:

1. ln a fuelmetering unit adapted for use in an internal combustion engine having an exhaust pipe which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an air-measuring device mounted in said suction tube upstream of said throttle valve, by-pass means connected with said suction tube both upstream and downstream of said airmeasuring device thereby bypassing said air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through said suction tube past said air-measuring device, the improvement comprising: a solenoid valve; control valve means associated with said by-pass means and adapted for controlling opening of said by-pass means and thereby the amount of air passing said air-measuring device thereby varying the proportionality of fuel and air in dependence on characteristic engine data; and an exhaust gas-measuring probe adapted to be mounted in said exhaust pipe and adapted for controlling said control valve means, wherein:

said control valve means comprises control conduit means opening into said suction pipe and a by-pass valve adapted for pneumatic actuation via said control conduit means; and

said solenoid valve is interposed in said control conduit means and is controlled by said exhaust gasmeasuring probe.

2. The improvement as described in claim 1, wherein said by-pass valve is a membrane valve.

3. The improvement as described in claim 1, wherein said control conduit means open into said suction tube downstream of said throttle valve.

4. The improvement as described in claim 1, wherein said throttle valve has a flap portion moving against the air flow through said suction tube when the position of said throttle valve in the latter is opened, said by-pass means opening in said suction tube upstream of said throttle valve and within the reach of said flap portion moving against said air flow, whereby, when said throttle valve is being opened, the air pressure prevailing in said suction tube downstream of said throttle valve also prevails at the opening of said by-pass means in said suction tube.

5. The improvement as described in claim 4, wherein said by-pass means comprise throttle means disposed at the opening of said by-pass means into said suction tube.

6. The improvement as described in claim 5, wherein the internal cross-sectional area of said throttle means is circular, rectangular or oval.

7. The improvement as described in claim 5, wherein said throttle means have two orifices opening into said suction tube successively in the direction of air flow.

8. In a fuel-metering unit adapted for use in an internal combustion engine having an exhaust pipe which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an air-measuring device mounted in said suction tube upstream of said throttle valve, by-pass means connected with and opening into said suction tube both upstream and downstream of said air-measuring device thereby bypassing said air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through said suction tube past said airmeasuring device, the improvement comprising: a solenoid valve; control valve means associated with said.

by-pass means and adapted for controlling opening of said by-pass means and thereby the amount of air passing said air-measuring device thereby varying the pro- 6 portionality of fuel and air in dependence on characteristic engine data; and an exhaust gas-measuring probe adapted to be mounted in said exhaust pipe and adapted for controlling said control valve means, wherein:

said control valve means comprises control conduit means opening into said suction pipe and a by-pass valve connected in said by-pass means at a location remote from the opening of the bypass means downstream of said air-measuring device, said bypass valve being adapted for pneumatic actuation via said control conduit means; and said solenoid valve is interposed in said control conduit means and is controlled by said exhaust gasmeasuring probe. 

1. In a fuel-metering unit adapted for use in an internal combustion engine having an exhaust pipe which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an air-measuring device mounted in said suction tube upstream of said throttle valve, by-pass means connected with said suction tube both upstream and downstream of said airmeasuring device thereby bypassing said air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through said suction tube past said air-measuring device, the improvement comprising: a solenoid valve; control valve means associated with said by-pass means and adapted for controlling opening of said by-pass means and thereby the amount of air passing said air-measuring device thereby varying the proportionality of fuel and air in dependence on characteristic engine data; and an exhaust gas-measuring probe adapted to be mounted in said exhaust pipe and adapted for controlling said control valve means, wherein: said control valve means comprises control conduit means opening into said suction pipe and a by-pass valve adapted for pneumatic actuation via said control conduit means; and said solenoid valve is interposed in said control conduit means and is controlled by said exhaust gas-measuring probe.
 2. The improvement as described in claim 1, wherein said by-pass valve is a membrane valve.
 3. The improvement as described in claim 1, wherein said control conduit means open into said suction tube downstream of said throttle valve.
 4. The improvement as described in claim 1, wherein said throttle valve has a flap portion moving against the air flow through said suction tube when the position of said throttle valve in the latter is opened, said by-pass means opening in said suction tube upstream of said throttle valve and within the reach of said flap portion moving against said air flow, whereby, when said throttle valve is being opened, the air pressure prevailing in said suction tube downstream of said throttle valve also prevails at the opening of said by-pass means in said suction tube.
 5. The improvement as described in claim 4, wherein said by-pass means comprise throttle means disposed at the opening of said by-pass means into said suction tube.
 6. The improvement as described in claim 5, wherein the internal cross-sectional area of said throttle means is circular, rectangular or oval.
 7. The improvement as described in claim 5, wherein said throttle means have two orifices opening into said suction tube successively in the direction of air flow.
 8. In a fuel-metering unit adapted for use in an internal combustion engine having an exhaust pipe which unit comprises an air-intake suction tube, a randomly adjustable throttle valve therein, an air-measuring device mounted in said suction tube upstream of said throttle valve, by-pass means connected with and opening into said suction tube both upstream and downstream of said air-measuring device thereby bypassing said air-measuring device and means for metering fuel in amounts substantially proportional to the amount of air flowing through said suction tube past said air-measuring device, the improvement comprising: a solenoid valve; control valve means associated with said by-pass means and adapted for controlling opening of said by-pass means and thereby the amount of air passing said air-measuring device thereBy varying the proportionality of fuel and air in dependence on characteristic engine data; and an exhaust gas-measuring probe adapted to be mounted in said exhaust pipe and adapted for controlling said control valve means, wherein: said control valve means comprises control conduit means opening into said suction pipe and a by-pass valve connected in said by-pass means at a location remote from the opening of the by-pass means downstream of said air-measuring device, said by-pass valve being adapted for pneumatic actuation via said control conduit means; and said solenoid valve is interposed in said control conduit means and is controlled by said exhaust gas-measuring probe. 